1. Field of Invention
The present invention relates to stringing of wire rope or cable.
2. Description of Prior Art
Customarily, one or more inactive cables have been strung along with the active lines in electrical power transmission networks for the purpose of lightning protection. The inactive cables were formed from helically wound steel wires and were often called wire ropes.
The cables were installed by a process known as being strung. While being strung, the cables were spooled from a reel and passed over stringing blocks or pulleys on distribution towers or poles. Due to their helically wound construction, the wires in these cables had an inherent tendency to rotate or twist in response to uncoiling forces as they were being spooled from the reel during stringing.
Fiberoptic rods clad in protective metal tubes have been included in the core along the central axis of these inactive cables for telemetry and relaying purposes. The tendency of the outer wires in the cable to uncoil while being strung caused problems with the fiberoptic rods. If the outer portions of the cable twisted more than a certain amount, the fiberoptic rods would break due to the twisting forces. It was felt that there was a limit, of no more than two or so 360.degree. rotations of the cable in one mile of cable, beyond which the integrity of the fiberoptic rod would be unreliable. Twisting problems were particularly compounded when the cable was being strung over an angular or irregular course where corners or turns were present.